This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-357788, filed Nov. 24, 2000, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a pattern defect inspection technique which inspects the presence of the defect of the pattern formed on, for example, photomask etc. The present invention relates to a pattern inspection device and a pattern inspection method to inspect presence of a defect of a pattern, especially a defect of square opening pattern called as a contact pattern and a mask manufacturing method.
2. Description of the Related Art
A usual pattern defect inspection device detects a defect of the pattern to be inspected by comparing the image data of the pattern to be inspected formed on the photomask etc. (Hereinafter, called as a xe2x80x9cSensor dataxe2x80x9d) with the data to which the position data is added to the design data used when the image pattern are designed (Hereinafter, called as a xe2x80x9cReference dataxe2x80x9d).
The configuration of the conventional pattern defect device is described to U.S. Pat. No. 5,574,800, for example.
The defect part of the object to be inspected is output by comparing the sensor data and the reference data obtained with the device described to U.S. Pat. No. 5,574,800 by the comparison circuit. The comparison circuit detects the defect part of the object to be inspected by comparing the sensor data and the reference data and performing the difference arithmetic.
In a word, the comparison circuit detects the defect part of the object to be inspected by obtaining a value obtained by subtracting the sensor data from the reference data, that is, the difference of the level between both data to be compared, and judging the presence of the defect by the threshold value of + and/or xe2x88x92 to the result.
However, the above-mentioned conventional pattern defect inspection device has the following problems. The signal level of an opening part obtained by the sensor does not rise to a sufficient bright level according to the influence of the optical resolution, when the square pattern width of the opening of the background becomes small for dark part. With this reason, when the square opening pattern with small pattern width is inspected by the level comparison, a level difference to the reference data is detected though there is no defect. Therefore, when the defect is detected, a normal pattern is mis-recognized as the defect. An example will be specifically explained as follows.
FIG. 1A to FIG. 1D are schematic diagrams to explain the problem in the conventional inspection device. FIG. 1A is a figure which shows the sensor data of the square pattern openings whose widths are 3 xcexcm, 1 xcexcm, 0.9 xcexcm, 0.8 xcexcm, and 0.7 xcexcm, respectively.
The sensor data is data in which the image imaged on the sensor face by the optical system of the pattern defect inspection device is electrically converted. Therefore, there is a case that the signal level of an opening part obtained by the sensor does not rise to a predetermined bright level by the influence of optical resolution.
When the section profile is taken at the center of the pattern, in each reference data corresponding to the above-mentioned opening data in FIG. 1B, the signal level of the bright part thereof is constant regardless of the width of the pattern. However, the signal level of the bright part of the sensor data has a tendency to fall as the width of the pattern narrows as shown in FIG. 1C. FIG. 1D is a figure which shows the section profile of the difference between the reference data and the sensor data corresponding to each opening data. In square opening patterns of 0.8 xcexcm and 0.7 xcexcm widths whose pattern widths are small as shown in FIG. 1D, a level difference is occurred.
Therefore, even in a normal pattern, the level difference with the reference data is occurred when a square opening pattern whose pattern width is width is inspected even though there is no defect, when the signal levels of the reference data and the sensor data are compared with the level comparison circuit of the pattern defect inspection device. Therefore, there is a disadvantage to mis-recognize the defect pattern even if it is a normal pattern when the defect of the pattern is detected.
According to embodiments of the present invention, a pattern inspection device and a pattern inspection method capable of accurately detecting a pattern defect even by an inspection of a square opening pattern whose pattern width is small and a mask manufacturing method are provided.
A pattern inspection device according to an aspect of present invention is characterized by comprising: means for obtaining a sensor data by imaging a pattern formed on an object to be inspected; reference data creation means for creating a reference data obtained from a design data of the pattern; pattern recognition means for cutting out a predetermined area from the reference data and recognizing a pattern; and level conversion means for converting a level of one of the reference data and the sensor data according to a recognition result in the pattern recognition means.
A pattern inspection method according to an aspect of present invention is characterized by comprising: imaging a pattern formed on an object to be inspected and obtaining a sensor data; obtaining a reference data from a design data of the pattern; recognizing the object to be inspected from the reference data by a recognition window with a plurality of detection points; calculating a light quantity of a recognized pattern of the object to be inspected; and converting a light quantity level of the reference data or the sensor data by using a light quantity of the reference data.
A mask manufacturing method according to an aspect of present invention is characterized by comprising: a step of forming a film on a substrate; a drawing step of drawing the pattern on the film; and a inspection step of inspecting the pattern by comparing a sensor data obtained by imaging the pattern and a reference data obtained from a design data of the pattern, in which the inspection step includes: a substep of recognizing an object to be inspected from the reference data by a recognition window having a plurality of detection points; a substep of calculating a light quantity of a recognized pattern of the object to be inspected; and a substep of converting a light quantity level of the reference data or the sensor data by using a light quantity of the reference data.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.